Study On Viscosity Model And Structure Of CaO-SiO₂-FeO-Cr₂O₃-MgO-MnO Slag

Chromium is an important alloy element in many metal materials.In the process of converter smelting chromium containing metals,chromium can easily be oxidized to Cr₂O₃.The Cr₂O₃ entering the slag will form high melting point chromium containing spinel phase with other components of the slag.This will affect the phase composition and slag structure of the slag system,thereby changing the properties of the slag and ultimately having an important impact on the physicochemical reaction of the converter smelting process.In some smelting processes of chromium containing hot metal converters,some steel mills have problems such as slag viscous,sticking guns,and back drying,which seriously affects the direct smelting process of the converter.In this paper,the CaO-SiO₂-FeO-Cr₂O₃-MgO-MnO chromium containing slag system of the begining and medium stage of converter was studied,and the researches work on the activity,phase composition,viscosity model and slag structure of the slag system were carried out.Wishing to provide some theoretical guidance for the actual chromium containing hot metal in converter smelting process.The main works and conclusions of this paper are as follows:Based on the theory of molecular-ion coexistence,the calculation model of slag system mass action concentration?activity?of CaO-SiO₂-FeO-Cr₂O₃-MgO-MnO slag after equilibrium at 1500°C was constructed.The calculation results show that the dibasic silicate oxide,ternary silicate oxide and chromium containing spinel oxide with higher activity in slag are Ca₂SiO₄ and CaSiO₃,CaMgSiO₄ and Ca₃MgSi₂O₈,MgCr₂O₄and FeCr₂O₄,respectively.With the increasing of Cr₂O₃ content,the activity of CaO,FeO,MgO and MnO decrease,the activity of Cr₂O₃ increases,and the activity of SiO₂does not change much.With the increasing of FeO,the activity of CaO,MgO,MnO,SiO₂ and Cr₂O₃ decrease and the activity of FeO increases.With the increasing of bacisity?CaO/SiO₂?,the activity of FeO,SiO₂ and Cr₂O₃ decrease,the activity of CaO and MgO increase,and the activity of MnO increases first and then decreases.The phase composition of the experimental slag system in the range of smelting temperature of 1300-1700°C was simulated by FactSage thermodynamics software.The phase composition of slag at 1500°C was analyzed by XRD.The influence of Cr₂O₃,FeO and bacisity on the phase composition of slag were analyzed.The influence law of the phase composition.The results show that when Cr₂O₃ is contained in the slag system,the phases contain MgCr₂O₄,FeCr₂O₄ and MgFe₂O₄ spinel phases,this is consistent with the calculation results of molecular-ion coexistence theory.The total content of spinel phase increases with the increasing of Cr₂O₃ and bacisity.When the temperature is 1300-1500°C,the content of spinel in the slag increases with the increasing of FeO.When the temperature is 1500-1700°C,the content of spinel decreases slightly with the increasing of FeO.The viscosity of the experimental slag system were calculated by seven common homogeneous viscosity model of Urbain,Ribound,NPL,Pal,Seshadri,Shankar and Iida.Based on this,using Einstein,Kunitz,Mooney,Chong,Roscoe,Einstein-Roscoe and Liu seven heterogeneous viscosity model to calculate the slag viscosity,and compared with the experimentally measured viscosity.Through the above calculations a heterogeneous viscosity prediction model suitable for the system was established.The results show that the Iida homogeneous model is more suitable for calculating the viscosity?₀ of the liquid phase of the slag.When the Cr₂O₃,FeO and bacisity change in the slag,the slag viscosity value calculated by using the newly established Liu-I heterogeneous viscosity model is consistent with the experimentally measured viscosity value.By calculating the??optical bacisty?,NBO/T and Q parameters of the slag system polymerization degree,the slag structure was analyzed by Raman spectroscopy to study the influence of slag composition on its structure.The theoretical calculation results show that as the content of Cr₂O₃ in the slag increases,the?and NBO/T decrease,Q increases.As the FeO content in the slag increases,the?and NBO/T increase,Q decreases.As the bacisity increases in the slag,?and NBO/T increase,and Q decreases.The results of Raman spectroscopy show that with the increasing of Cr₂O₃ content in slag,Q⁰+Q¹ decreases,Q²+Q³ increases,?Q²+Q³?/?Q⁰+Q¹?increases,NBO/Si decreases,and the degree of polymerization of slag increases.As the FeO content and bacisity,Q⁰+Q¹ increase,Q²+Q³ decreases,?Q²+Q³?/?Q⁰+Q¹?decreases,NBO/Si increases,and the degree of polymerization of slag decreases.